[C# Solution] Base Class Does Not Contain a Constructor That Takes 0 Arguments
Recently, I encountered an error while creating a constructor in a derived class. The error and code is given below.
Error:
Error 1 ‘Hello_World.Customer’ does not contain a constructor that takes 0 arguments
using System;
namespace Hello_World
{
class Customer
{
public string _name;
public Customer(string name)
{
_name = name;
}
public void PrintName()
{
Console.WriteLine(_name);
}
}
class Customer2 : Customer
{
//Error
public Customer2(string name)
{
_name = name;
}
}
class Program
{
static void Main(string[] args)
{
Customer2 cust = new Customer2("Robert Marks");
cust.PrintName();
}
}
}
I tried my best to analyze the issue, but somehow I was not able to figure out that why derived class is not allowing me to create a constructor and showing this annoying error. After doing a little search over internet, I finally found the solution.
The problem was that I did not know the fact that whenever you try to call a constructor in derived class, then by default a base class parameterless constructor is called first. Also, if you are creating a custom constructor in base class, then your default base class parameterless constructor will be overridden. Now, in this case, there are 2 solutions. First solution, you need to explicitly create a base class parameterless constructor. Second solution, while creating your derived class constructor, you need to call a base class custom constructor using base keyword and passing required parameters to it. Examples for both solutions are given below.
First Solution : Parameterless Constructor
using System;
namespace Hello_World
{
class Customer
{
public string _name;
//Solution 1: Custom Constructor with 0 Arguements
public Customer()
{
}
public Customer(string name)
{
_name = name;
}
public void PrintName()
{
Console.WriteLine(_name);
}
}
class Customer2 : Customer
{
//Error
public Customer2(string name)
{
_name = name;
}
}
class Program
{
static void Main(string[] args)
{
Customer2 cust = new Customer2("Robert Marks");
cust.PrintName();
}
}
}
Second Solution : Calling Base Class Constructor
using System;
namespace Hello_World
{
class Customer
{
public string _name;
public Customer(string name)
{
_name = name;
}
public void PrintName()
{
Console.WriteLine(_name);
}
}
class Customer2 : Customer
{
//Solution 2: Calling Base Class Constructor using Base keyword and passing required
// parameter
public Customer2(string name) : base(name)
{
}
}
class Program
{
static void Main(string[] args)
{
Customer2 cust = new Customer2("Robert Marks");
cust.PrintName();
}
}
}
